Does miso paste contain soy?

December 24, 2025 •

3 min read

With its origins tracing back over 1,300 years in Japanese culture, miso is a staple fermented food known for its rich, umami flavor. For those with dietary concerns, the fundamental question arises: Does miso paste contain soy? Understanding the fermentation process is key to knowing the answer.

Quick Summary

Most traditional miso is made from fermented soybeans, koji, and salt, but many different varieties exist using other grains like rice or barley. Soy-free options, including those made from chickpeas or adzuki beans, are increasingly available for those with allergies.

Key Points

Soy is a Primary Ingredient: Most traditional miso paste is made by fermenting soybeans along with salt and a grain-based koji starter.
Soy-Free Alternatives Exist: For those with soy allergies, products labeled as "soy-free," like chickpea or adzuki bean miso, offer safe alternatives.
Miso Varieties Differ: The ratio of ingredients and fermentation time affect the flavor and color of miso, from mild white miso to intense hatcho miso.
Always Read Labels: If you have a soy allergy, it is essential to read the ingredient list carefully, as soy-based miso contains allergens even after fermentation.
Koji Varies Too: The koji starter can be made from rice, barley, or soybeans, further influencing the final miso product.
Fermentation Doesn't Remove Allergens: The breakdown of proteins during fermentation does not eliminate the soy allergen, so soy-based miso is not safe for those with an allergy.

Miso's Foundational Ingredients: Soybeans and Koji

At its core, miso is a fermented paste, and for the vast majority of commercially available varieties, soybeans are a primary ingredient. The process involves combining cooked, mashed soybeans with salt and koji. Koji is a cultivated mold (Aspergillus oryzae) grown on a grain like rice, barley, or even soybeans themselves. It is the koji's enzymes that initiate the fermentation, breaking down the soybeans' proteins and starches into readily digestible amino acids and sugars, which develops miso's distinct, savory umami flavor.

The ratio of soybeans to grain koji and the duration of fermentation are the key factors that produce the incredible diversity of miso types. For example, a shorter fermentation with a higher rice koji ratio yields a sweeter, lighter paste like white miso, while a longer fermentation with more soybeans creates a darker, saltier paste such as red miso.

The Variety of Miso and Its Soy Content

Not all miso is created equal, and while soy is traditional, it is not an absolute requirement for all miso-like products. Miso is broadly categorized by its color and ingredients:

White Miso (Shiro Miso): Made with a higher proportion of rice koji and fermented for a shorter period, resulting in a sweet, mild flavor and off-white to yellowish color. It still contains soybeans.
Yellow Miso (Shinsu Miso): Fermented for a slightly longer time than white miso, with a golden-yellow hue and a mild, adaptable flavor. It typically contains soybeans and rice or barley koji.
Red Miso (Aka Miso): Made with a higher ratio of soybeans, less koji, and aged for longer. The result is a richer, saltier flavor and a deep reddish-brown color. Soybeans are a key component.
Barley Miso (Mugi Miso): This rustic miso is made with barley koji and soybeans. It has a strong, malty aroma and is often fermented longer than white miso. Contains soybeans.
Hatcho Miso (Mame Miso): This is a unique type of miso made almost exclusively from soybeans and soybean koji, fermented for up to three years. It has an intense, dark color and a very robust flavor, and is especially high in soy content.

Soy-Free Miso Alternatives

For those with soy allergies, modern food producers have created excellent soy-free alternatives. These products replicate the umami and texture of traditional miso by fermenting other legumes or seeds with koji.

Common soy-free options include:

Chickpea Miso: A popular choice that mimics the texture and flavor profile of traditional miso very well.
Adzuki Bean Miso: Another alternative bean used in place of soybeans for fermentation.
Nut or Seed-Based Miso: Some specialty producers experiment with ingredients like sunflower seeds or pumpkin seeds to create unique, flavorful miso substitutes.

Comparison Table: Miso Varieties and Soy Content


Miso Type	Key Ingredients	Soy Content	Flavor Profile	Common Uses
White Miso	Soybeans, Rice Koji, Salt	Yes	Sweet, Mild, Creamy	Dressings, Sauces, Light Soups
Red Miso	Soybeans, Grain Koji, Salt	Yes	Salty, Rich, Umami-forward	Hearty Soups, Marinades, Glazes
Barley Miso	Soybeans, Barley Koji, Salt	Yes	Earthy, Malty, Robust	Soups, Stews, General Seasoning
Hatcho Miso	Soybeans, Soybean Koji, Salt	Yes (Exclusive Soy)	Intense, Pungent, Smoky	Rich Broths, Condiment, Glazes
Chickpea Miso	Chickpeas, Grain Koji, Salt	No	Savory, Mild, Similar to White Miso	Dressings, Soups, Marinades

Label Reading and Dietary Precautions

For anyone with a soy allergy or intolerance, reading the product label is crucial. Unless specifically labeled as "soy-free," you should assume that miso paste contains soy. Even products made with other grains like barley still use soybeans as the foundation. The fermentation process breaks down some of the soy proteins, but not enough to eliminate allergens. While the fermentation can produce beneficial bacteria and reduce anti-nutrients, the inherent soy allergen remains present in soy-based miso.

Outbound Link

For more information on the science behind miso and umami, visit the Umami Information Center.

Conclusion: The Bottom Line on Miso and Soy

The vast majority of traditional miso paste varieties are made from fermented soybeans, making them unsuitable for those with soy allergies. However, the world of fermentation is expansive, and innovation has led to the creation of excellent soy-free alternatives using ingredients like chickpeas and other beans. By understanding the different types of miso and their primary ingredients, consumers can make informed choices based on their dietary needs. Always check the label for confirmation, especially when navigating allergies. For everyone else, embracing the variety of miso, from sweet white to potent hatcho, is a flavorful culinary journey worth taking.

Frequently Asked Questions

No, while most traditional and common varieties contain soybeans, specialty and modern alternatives are made using other legumes, such as chickpeas or adzuki beans.

Both white and red miso are made with soybeans, but they differ in their ratio of koji to soybeans and their fermentation time, which affects color and flavor, not the presence of soy.

Yes, chickpea miso is a popular and flavorful substitute for traditional soy-based miso. It offers a similar umami profile and texture, making it a great option for soy-free cooking.

No, most miso varieties contain soy and should be avoided by individuals with a soy allergy. Always check for a 'soy-free' label when purchasing alternatives.

Miso is traditionally made by combining cooked soybeans, salt, and koji (a mold cultivated on grains like rice or barley). The mixture is then fermented for months or even years.

No, the fermentation process breaks down some soy proteins but does not completely eliminate the soy allergen. Soy-based miso is not safe for those with a soy allergy.

Koji is the fermentation starter, a mold that produces enzymes that break down the proteins and starches in soybeans and grains. This process creates miso's characteristic umami flavor.